#define _CRT_SECURE_NO_WARNINGS 1
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'

void solve() {
	int n; cin >> n;
	int a[200010] = { 0 };
	while (n--) {
		int x; cin >> x;
		cout << char('a' + a[x]);
		a[x]++;
	}
	cout << endl;
}

int main() {
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	int t; cin >> t;
	while (t--) {
		solve();
	}
	return 0;
}